Microsoft Wpf Silverlight Comparison Whitepaper V1 1

Silverlight / WPF Comparison Whitepaper.

Programmatic Differences
Between Silverlight and WPF

A Whitepaper by Wintellect, LLC
Version 1.1
Build 0000

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Programmatic Differences Between Silverlight and WPF – A Whitepaper Page 1 of 70
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TABLE OF CONTENTS

Table of Contents ...............................................................................................................................2
Introduction ......................................................................................................................................5
Similarities Between Silverlight and WPF ............................................................................................5
Dependency Properties .......................................................................................................................... 6
Controls .................................................................................................................................................. 6
Animations .............................................................................................................................................. 7
Custom Controls ..................................................................................................................................... 7
User Controls ...................................................................................................................................... 8
Video ....................................................................................................................................................... 8
Ink and Stylus .......................................................................................................................................... 9
Differences Between Silverlight and WPF ...........................................................................................9
Architecture ............................................................................................................................................ 9
Deployment .......................................................................................................................................... 10
BAML/XAML ...................................................................................................................................... 10
XAML..................................................................................................................................................... 11
XAML Language................................................................................................................................. 11
Triggers ............................................................................................................................................. 12
Visual State Manager ........................................................................................................................ 13
Markup Extensions ........................................................................................................................... 14
User Interface ....................................................................................................................................... 15
Keyboard ........................................................................................................................................... 16
Mouse ............................................................................................................................................... 17
IsEnabled........................................................................................................................................... 19
Local File Access ................................................................................................................................ 20
Sub-Pixel Rendering .......................................................................................................................... 20
Font Support ..................................................................................................................................... 21
Graphics ............................................................................................................................................ 22
Kiosks ................................................................................................................................................ 24
Object Trees ...................................................................................................................................... 25
Control Library ...................................................................................................................................... 27
General ................................................................................................................................................. 30
Routed Events ................................................................................................................................... 30

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Data-Binding ..................................................................................................................................... 30
Networking ....................................................................................................................................... 35
Local Isolated Storage ....................................................................................................................... 37
Resource Dictionaries ....................................................................................................................... 39
Custom Dependency Properties ....................................................................................................... 40
Commanding ..................................................................................................................................... 41
.Net Framework .................................................................................................................................... 41
Collections ........................................................................................................................................ 41
Cryptography .................................................................................................................................... 42
Threading .......................................................................................................................................... 43
WPF Specific Functionality ............................................................................................................... 44
Desktop Functionality ........................................................................................................................... 44
Printing ............................................................................................................................................. 44
XPS Documents ................................................................................................................................. 44
Speech .............................................................................................................................................. 46
InterOp .............................................................................................................................................. 47
XAML..................................................................................................................................................... 48
Styles ................................................................................................................................................. 48
User Interface ....................................................................................................................................... 49
3D Graphics ....................................................................................................................................... 49
Themes ............................................................................................................................................. 49
Skins .................................................................................................................................................. 50
Image Manipulation .......................................................................................................................... 50
Page-Based Navigation ..................................................................................................................... 51
Input Gestures .................................................................................................................................. 52
General Functionality ............................................................................................................................ 53
Freezable Objects.............................................................................................................................. 53
Data Providers................................................................................................................................... 53
Validation .......................................................................................................................................... 54
Dynamic Resources ........................................................................................................................... 57
Code Access Security......................................................................................................................... 57
Silverlight Specific Functionality ....................................................................................................... 58
Web Functionality ................................................................................................................................. 58
Browser InterOp ............................................................................................................................... 58
Media .................................................................................................................................................... 60

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Traditional Streaming........................................................................................................................ 60
Progressive Download ...................................................................................................................... 60
Smooth Streaming ............................................................................................................................ 60
Timeline Markers .............................................................................................................................. 61
Deep Zoom ........................................................................................................................................... 62
Code Reuse Strategies ...................................................................................................................... 63
User Controls ........................................................................................................................................ 63
Compiler Directives ............................................................................................................................... 63
Linked Files ........................................................................................................................................... 64
Coding Scenarios ................................................................................................................................... 65
Element-to-Element Binding ............................................................................................................. 65
Multi-Data Binding ............................................................................................................................ 67
Triggers / Visual State Manager ........................................................................................................ 68
Fonts ................................................................................................................................................. 69
Summary ......................................................................................................................................... 70

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INTRODUCTION
The Windows Presentation Foundation (WPF) is Microsoft’s latest development platform for building
next-generation Windows client applications. Silverlight, a subset of WPF, extends the platform to the
web via the add-on mechanism available in most current browsers. As a subset of WPF, the ability to
create rich Internet applications is unprecedented; however, there are some significant differences
between the capabilities of Silverlight and WPF, as well as important differences in the programming
features of the two technologies.

There are several architectural reasons for the discrepancies between WPF and Silverlight. First and
foremost is that Silverlight 2 is a downloadable plug-in running within a browser. In order to insure that
the plug-in is a small as possible, Microsoft built a smaller version of the .Net Framework, one that is
highly optimized for size and is a small subset of the full .NET Framework, to embed within it. WPF, on
the other hand, has full access to the main .Net Framework and all its associated assemblies. The
difference between the smaller, downloadable .Net Framework and the full desktop version is one of
the major disparities between the two platforms. In addition, the fact that Silverlight is rooted within
the browser, and inherits the limitations of that environment, further differentiates the two platforms.

This whitepaper documents both the identical (or nearly so) functionality as well as the differences.
WPF and Silverlight have many technological concepts in common: Dependency Properties, Data
Binding, Custom Controls and Animation to name a few. In addition, this paper documents
functionality implementations that may be available in only one technology or the other. For example,
WPF implements a large library of controls for document handling, including printing and formatting
large documents.

Finally, this whitepaper outlines some strategies in obtaining code reuse across both technologies. Due
to minor differences in implementations of common elements, developers need to carefully plan their
development in order to reuse code in both platforms. Of course, since certain functionality may not
exist in one platform, developers may need to reduce the scope of the application in those cases.

One last note about this whitepaper: where appropriate, some information about the future version of
Silverlight 3 has been provided. Please note that Silverlight 3 is currently in beta and any information
may be subject to change. In addition, more Silverlight 3 information can be found at
www.silverlight.net.

SIMILARITIES BETWEEN SILVERLIGHT AND WPF
Silverlight is generally considered to be a subset of WPF. There are very few pieces of functionality that
exist solely within the Silverlight platform. That stated, though the two platforms have their differences,
much of the implementations are similar.

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DEPENDENCY PROPERTIES
Dependency properties are a key foundation for both Silverlight and WPF. Both platforms
implement dependency properties in nearly identical ways; WPF allows for slightly more fine
tuning the metadata when registering a dependency property.

The template for defining a dependency property looks as follows:

C#

public string MyProperty
{
get { return (string)GetValue(MyPropertyProperty); }
set { SetValue(MyPropertyProperty, value); }
}

public static readonly DependencyProperty MyPropertyProperty =
DependencyProperty.Register("MyProperty", typeof(string),
typeof(MyClass), new PropertyMetadata(""));

VISUAL BASIC

Property MyProperty() As String
Get
Return CType(GetValue(MyPropertyProperty), String)
End Get
Set(ByVal value As String)
SetValue(MyPropertyProperty, value)
End Set
End Property

Public Shared ReadOnly MyPropertyProperty As DependencyProperty = _
DependencyProperty.Register("MyProperty", GetType(String), _
GetType(MyCustomClass), New PropertyMetadata(""))

In essence, the backing store of a standard class’ property is an object of type
DependencyProperty instead of what would normally be a private field. By convention, the
backing store appends the word “Property” to the end of the actual class’ property name.

The Register() static method accepts a class of type PropertyMetadata that, among other things,
sets the default value of the property. The differences between Silverlight and WPF reside in
the metadata structure: Silverlight only supports the PropertyMetadata class here, while WPF
supports several classes (all derived from PropertyMetadata).

CONTROLS
Silverlight and WPF have a number of controls in common. Those controls not available in
Silverlight can usually be found in either the Silverlight SDK or the Silverlight Toolkit. However,
the implementation of the controls is not exactly the same in both platforms in most cases.

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Microsoft is committed to bringing both platforms closer in terms of supported controls and
functionality, and with each successive version the control libraries become more similar.

ANIMATIONS
Both Silverlight and WPF implement an animation mechanism. Animation is a complex topic, so
this paper will just focus on some of the rudimentary aspects of it. At a basic level, animation is
simply controlling a dependency property’s value through time. For instance, moving an
element from left to right involves changing its Canvas.Left property through time.

One way WPF and Silverlight implement this functionality is through linear interpolation, a
method of smoothly transitioning a property from one value to another over time. Below is a
snippet of XAML showing a simple animation declaration to move a button from left to right
over the course of one second.

<Storyboard x:Name="ButtonAnimation">
<DoubleAnimation
Storyboard.TargetName="MyButton"
Storyboard.TargetProperty="(Canvas.Left)"
Duration="0:0:1"
From="0"
To="200" />
</Storyboard>

There are many ways to initiate the animation: through triggers (for WPF), the
VisualStateManager (for Silverlight), EventTriggers within styles, or through procedural code.

The linear interpolation can be modified somewhat by adding AccelerationRatio and
DecelerationRatio properties to the animation. These attributes essentially create three linear
interpolations for the entire animation in order to modify the starting and stopping speeds. For
example, a designer would use these attributes to have an object gradually pick up speed or
stop suddenly. Unfortunately, Silverlight does not implement these two attributes, but the
effect can be duplicated using keyframe animations with linear interpolation.

For more complex animations, WPF and Silverlight support keyframe animations, a method of
animation specifying a value at a specific point in time (a keyframe). The animation system then
interpolates the transition from one keyframe to the next. The method of interpolation can be
as simple as a basic linear method seen before, discrete (that is, no interpolation), or more
complex spline interpolations.

One aspect of animation present in WPF is path-based animations. Silverlight, unfortunately,
does not have the facility to animate an object along a pre-defined path.

CUSTOM CONTROLS
Due to the styling and templating capabilities of WPF and Silverlight, the need for custom and
user controls is less than in older technologies. However, there are scenarios when the

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development of such a control becomes necessary; such as when no existing control supports
the required functionality needed.

WPF and Silverlight define two types of user creatable controls: user controls and custom
controls. User controls can be thought of as composite controls while custom controls are
either derived from existing controls or are something completely new and derived from the
Control base class itself.

See http://msdn.microsoft.com/en-us/magazine/cc721611 for a great article on creating custom
controls within Silverlight.

User Controls

User controls are useful when needing to reuse a complex group of elements in multiple places
within an application or across applications. User controls typically derive from the UserControl
element and can be declared in XAML as follows:

<UserControl
x:Class="MyProject.MyUserControl"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x=http://schemas.microsoft.com/winfx/2006/xaml
>



</UserControl>

VIDEO
There are a few controls to play video resources in WPF and Silverlight. The MediaPlayer class is
the major element in playing video from within an application. The MediaPlayer class wraps the
functionality of Windows Media Player and therefore supports all the file formats that it does
(such as .wmv, .avi, and .mpg). However, the MediaPlayer class is used from procedural code
only and has no provision for XAML markup. Additionally, the MediaPlayer class is only available
within WPF.

To declaratively use video in WPF or Silverlight, the MediaElement class is a FrameworkElement.
Within WPF, the MediaElement wraps the functionality of MediaPlayer, which in turn wraps the
Windows Media Player. However, since the MediaPlayer class does not exist in Silverlight the
MediaElement is completely separate from any local media player.

The following snippet shows a method for embedding video into a XAML page:

<MediaElement Width="640" Height="480" Source="MyVideo.wmv" />

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Since the MediaElement is a Framework element, it supports many options to control its look-
and-feel. In addition, within WPF only, a MediaElement can be contained within a VisualBrush
and be used to “paint” any UIElement’s brush properties (i.e. background, 3D surfaces, etc.).

INK AND STYLUS
Digital ink refers to a method of input using a stylus on a touch-sensitive surface. Tablet PCs,
pressure-sensitive tablets, touch screens, and other electronic devices have the capability to
create digital ink. In addition, the mouse may also be used as a stylus device, though it is
generally more difficult to use in that manner.

WPF defines stylus-based input to distinguish between the traditional mouse and one of the
touch-based input devices (where the input mechanism could be a digital pen or even a finger).

A special panel called an InkCanvas is the main element used to accept free-form ink input. The
InkCanvas is useful for adding annotations to images and documents.

WPF supports ink-based gestures as well found in the System.Windows.Ink.ApplicationGesture
enumeration. These gestures allow a user to control a system using only the stylus to perform
commands such as Up, Down, Cut, Paste, etc.

Finally, since WPF allows the capture of handwritten text there is a facility for handwriting
recognition. The class used to analyze handwriting is InkAnalyzer ; however, it requires adding
references to several assemblies found on Tablet PC systems: IAWinFX.dll, IACore.dll, and
IALoader.dll. In a Silverlight application, it is possible to get handwriting recognition through a
server-side component.

DIFFERENCES BETWEEN SILVERLIGHT AND WPF
Silverlight is a XAML-based technology that runs within the sandbox of browser plug-in. As such, it
implements a subset of both the .Net Framework and WPF functionality. Microsoft made the decision
to cut features to reduce the download footprint of the Silverlight plug-in. Future versions of Silverlight
will attempt to reduce the differences between the two platforms, and still retain a small download
footprint. Microsoft will accomplish this feat by only downloading libraries that the Silverlight
application actually uses.

ARCHITECTURE
The basic architecture of WPF is analogous to traditional WinForms development, with the
addition of the Media Integration Layer (MIL). The MIL is wrapped by two core assemblies,
Presentation Framework and Presentation Core. WPF applications are run on a Windows client
platform, and, with the exception of browser-hosted applications, are hosted by the system.

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Since WPF applications are run on the client, they have access to the full .Net Framework
programming stack, including the browser-hosted model.

Silverlight applications, on the other hand, run within the plug-in model of the hosted web
browser. The plug-in contains all the core code libraries that Silverlight needs to run. However,
in an effort to minimize the download time for installing Silverlight, the entire .Net Framework is
not loaded, instead, Microsoft created the Core CLR, a distinct subset of the .Net Framework
runtime libraries.

The differences between the two .Net Framework libraries constitute the major hurdles for
developers when building applications to run in both architectures. Shared libraries are not
capable of being shared between platforms since the core referenced assemblies are different.
Library assemblies must be targeted for one platform only; and therefore cannot be shared.
However, this whitepaper will discuss various alternate methods for sharing similar code
between the two platforms.

DEPLOYMENT
Obviously, there are significant differences in deploying a Silverlight application compared with
deploying a WPF application.

Silverlight applications are hosted within a web server and a web page. To minimize client
download size, Silverlight uses an XAP archive. A XAP archive is a zip-compressed archive of the
Silverlight application, plus a manifest file describing the content. Visual Studio automatically
generates the XAP archive when using the Silverlight project template.

WPF applications can be deployed as a standalone application, ClickOnce application, or a XAML
Browser application.

BAML/XAML
BAML is a binary form of the XAML in a WPF application. When compiled and deployed, the
text-based XAML is reconstituted into binary form for quicker processing. Technically, the XAML
is not compiled, just compacted into an efficient binary format, though one can argue the
semantics.

In order to retrieve the XAML of a page or control dynamically, it must be compiled as an
Embedded Resource. This will store the actual XAML as an embedded resource within the
assembly. It is then possible to retrieve the XAML in code via the resource manager.

C#

Stream s =
this.GetType().Assembly.GetManifestResourceStream("MyProject.MyControl.xaml");

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VISUAL BASIC

Dim s As Stream = _
Me.GetType.Assembly.GetManifestResourceStream("MyProject.MyControl.xaml")

XAML
The eXtensible Application Markup Language is a dialect of XML that both WPF and Silverlight
use to describe the user interface. Both platforms support a separate code-behind file to
contain .Net programming code to manipulate the elements and controls declared within the
XAML. The code-behind model is the same one first introduced with .Net at its inception to
provide a separation between procedural code and presentation.

XAML Language
Most of the XAML language is similar between WPF and Silverlight. Differences begin appearing
with the available UI elements available to each platform.

<UserControl x:Class="Sample"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
>
<Grid Background="LightGray">

</Grid>
</UserControl>

Silverlight does require that the root element contain a default “xmlns” namespace declaration,
whereas WPF can assume an implicit value.

Additional namespaces added to the root element must point to assemblies that are deployed
with the application. WPF applications can point to assemblies within the GAC or deployed
elsewhere.

TargetType
Some elements use a TargetType attribute to specify the type of element being referenced. For
example, Styles use TargetType to specify the type of element being styled. WPF can specify the
type using the {x:Type} markup extension, or by using the short-hand notation that relies on the
default TypeConverter for TargetType:

<Style x:Key="MyButtonStyle" TargetType="{x:Type Button}">
…
</Style>

Silverlight can only use this short-hand notation to specify the TargetType:

<Style x:Key="MyButtonStyle" TargetType="Button">

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…
</Style>

Triggers
WPF supports a trigger mechanism to respond to certain end-user actions, such as moving the
mouse over a UI element, or pressing a button. Triggers are usually defined as part of a style, as
follows:

<Style x:Key="Triggers" TargetType="{x:Type Button}">
<Style.Triggers>
<Trigger Property="IsPressed" Value="true">
<Setter Property="Foreground" Value="Green"/>
</Trigger>
</Style.Triggers>
</Style>

WPF supports multiple types of triggers, such as MultiTrigger, EventTrigger and DataTrigger.

MultiTrigger’s allow more than one condition to be specified before the style is applied. For
example,

<Style x:Key="Triggers" TargetType="{x:Type Button}">
<Style.Triggers>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsMouseOver" Value="true" />
<Condition Property="IsSelected" Value="true" />
</MultiTrigger.Conditions>

<Setter Property="Foreground" Value="Purple"/>
</MultiTrigger>
</Style.Triggers>
</Style>

EventTriggers are triggers that respond to RoutedEvents, and only activate animations, they
cannot properties on elements.

<EventTrigger RoutedEvent="Button.MouseEnter">
<EventTrigger.Actions>
<BeginStoryboard>
<Storyboard>
<DoubleAnimation
Duration="0:0:0.5"
Storyboard.TargetProperty="Opacity"
To="0.5" />
</Storyboard>
</BeginStoryboard>
</EventTrigger.Actions>
</EventTrigger>

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DataTriggers and MultiDataTriggers are triggers that respond to changes in the underlying data
bound to an element. An example of a DataTrigger,

<Style TargetType="{x:Type ListBoxItem}">
<Style.Triggers>
<DataTrigger Binding="{Binding Path=Amount}" Value="0">
<Setter Property="Foreground" Value="Red"/>
</DataTrigger>
</Style.Triggers>
</Style>

Since DataTriggers use the Binding syntax, more robust conditions can be specified through the
use of binding converters, allowing the application to reduce a range of values to a boolean
value. Additionally, the MultiDataTrigger, its syntax mirrors the MultiTrigger element, can be
used to further define conditions.

Silverlight, however, does not implement the trigger mechanism, but instead introduces a
concept called the Visual State Manager.

Visual State Manager
The Visual State Manager was introduced in Silverlight 2 to simplify control over visual states
and transitions. WPF does not currently implement the Visual State Manager, however, the
WPF Toolkit (http://wpf.codeplex.com), contains a preview of the VisualStateManager for WPF
in the March 2009 release.

Within a ControlTemplate, the Visual State Manager would be used to define any number of
visual states and effects.

<Canvas x:Name="MyCanvas">
<vsm:VisualStateManager.VisualStateGroups>
<vsm:VisualStateGroup x:Name="CommonStates">
<vsm:VisualStateGroup.Transitions>
<vsm:VisualTransition To="Normal" GeneratedDuration="0:0:0.2" />
<vsm:VisualTransition To="MouseOver" GeneratedDuration="0:0:0.5" />
</vsm:VisualStateGroup.Transitions>
<vsm:VisualState x:Name="Normal" />
<vsm:VisualState x:Name="MouseOver">
<Storyboard>
<ColorAnimation
Storyboard.TargetName="MyShape"
Storyboard.TargetProperty="(Shape.Fill).(SolidColorBrush.Color)"
To="Yellow"
Duration="0" />
</Storyboard>
</vsm:VisualState>
</vsm:VisualStateGroup>
</vsm:VisualStateManager.VisualStateGroups>



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Within the application code, the state can be changed by a simple call to the
VisualStateManager.
C#

void MyControl_MouseOver(object sender, MouseEventArgs e)
{
VisualStateManager.GoToState(this, "MouseOver", true);
}

VISUAL BASIC

Private Sub MyShape_MouseEnter(ByVal sender As System.Object, _
ByVal e As System.Windows.Input.MouseEventArgs)

VisualStateManager.GoToState(Me, "MouseOver", True)
End Sub

Note, however, that the VisualStateManager does not completely replace or duplicate the
functionality found in the Trigger mechanism. For example, there is no support for anything
similar to MultiTrigger or DataTrigger.

Markup Extensions
XAML processors support extensions to the markup language in order to provide additional
functionality not found within the default processing. For example, default processing accepts
literal values for attributes, but in some scenarios, the attribute should reference a previously
constructed object or access a static object.

The syntax for a XAML markup extension in an attribute is:

<ElementName Attribute="{MarkupExtension …}">

Markup extensions can also be used as a property element, and visually are indistinguishable
from the default element syntax. Markup extensions in the x: namespace (the default mapping
for XAML namespace) are XAML-defined markups and are not specific to WPF.

WPF has full support for markup extensions. The most notable are:
 StaticResource
 DynamicResource
 Binding
 RelativeSource
 TemplateBinding
 x:Type
 x:Static
 x:Null
 x:Array

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WPF also supports the creation of custom markup extensions. Custom markup extensions
should be named with the Extension suffix and derive from the MarkupExtension base class.

Silverlight implements limited support for markup extensions, using only x:Null, StaticResource,
Binding, and TemplateBinding. Also, since Silverlight doesn’t implement a public
MarkupExtension class, there is no support for custom markup extensions. The Binding markup
extension is the only extension that Silverlight supports that has a corresponding class accessible
via code.

Silverlight also doesn’t support the alternative syntax of adding the “Extension” suffix like WPF
does. So, {x:Null} is valid, but {x:NullExtension} is not.

Markup extensions, in Silverlight, can not specify constructor parameters by name. Therefore
{StaticResource myKey} is valid, but {StaticResource ResourceKey=myKey} is not.

USER INTERFACE
Most interaction between a user and the application occurs through the user interface as
events. In WPF and Silverlight, most events are Routed Events (see ROUTED EVENTS for more
information on the differences in Routed Events between Silverlight and WPF). Each event,
regardless of type, defines a delegate for handling purposes. The definition typically only varies
the event arguments passed to the handler.

C#

public delegate void RoutedEventHandler(
Object sender,
RoutedEventArgs e
)

VISUAL BASIC

Public Delegate Sub RoutedEventHandler ( _
sender As Object, _
e As RoutedEventArgs _
)

This definition, in essence, is the base definition for all other UI related events. All routed event
arguments derive from the base RoutedEventArgs class. This document will also discuss more
specific routed events (such as mouse or keyboard events) in detail, so knowing that there are
differences in the base class as well is important.

The table below shows the implementation of the RoutedEventArgs base class and the
differences between WPF and Silverlight.

ROUTEDEVENTARGS
Property WPF Silverlight
Device Yes No

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Handled Yes Yes
InputSource Yes No
OriginalSource Yes Yes
RoutedEvent Yes No
Source Yes No
Timestamp Yes No

The Handled property can be set in the event handlers to indicate to other listeners that the
event has been successfully handled already. In essence, setting the Handled property to true
would let other controls in the event hierarchy (either bubbled up, or tunneled down) know that
the event has been successfully handled. That stated, the other controls could potentially
ignore the fact and provide additional functionality.

Keyboard
Most UI elements support the KeyDown and KeyUp events. In both Silverlight and WPF, the
handler’s signature is:

C#

public delegate void KeyEventHandler(
Object sender,
KeyEventArgs e
)

VISUAL BASIC

Public Delegate Sub KeyEventHandler ( _
sender As Object, _
e As KeyEventArgs _
)

However there are some significant differences in between the implementations of
KeyEventArgs in the two technologies.

Property WPF Silverlight
ImeProcessedKey Yes No
IsDown Yes No
IsRepeat Yes No
IsToggled Yes No
IsUp Yes No
Key Yes Yes
KeyboardDevice Yes No
KeyStates Yes No
SystemKey Yes No
PlatformKeyCode No Yes

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In addition, the Key enumeration contains different values between Silverlight’s version and
WPF’s. For example, Silverlight contains Key.Alt to represent the Alt key, while WPF’s
enumeration contains Key.LeftAlt and Key.RightAlt.

WPF also exposed two additional event handlers, PreviewKeyDown and PreviewKeyUp, that
Silverlight does not implement.

Non-Windows Platforms
Microsoft released Silverlight plugins for both Windows and Mac OS X operating systems. WPF,
on the other hand, is only currently supported on the Windows platform.

There is a drive by the open source community to port Silverlight to Linux. The project,
Moonlight, only supports Silverlight 1.0, but the Silverlight 2.0 equivalent is under development.
Moonlight is a sub-project under the Mono umbrella (an attempt to port the entire .Net
Framework to Linux). Currently, there is no push for porting WPF itself to Linux through the
Mono project. See http://www.mono-project.com for more information.

Silverlight supports non-Windows key trapping through the use of the PlatformKeyCode value
returned as part of the KeyEventArgs class. However, the common Apple key on Mac platforms
is available through the ModifierKeys enumeration in Silverlight only.

Mouse
Both Silverlight and WPF support mouse events to various degrees. The following table
documents the different mouse events supported by the two platforms.

Mouse Event WPF Silverlight
LostMouseCapture Yes Yes
MouseDoubleClick Yes No
MouseDown Yes Yes
MouseEnter Yes Yes
MouseLeave Yes Yes
MouseLeftButtonDown Yes Yes
MouseLeftButtonUp Yes Yes
MouseMove Yes Yes
MouseRightButtonDown Yes No
MouseRightButtonUp Yes No
MouseUp Yes No
MouseWheel Yes No
PreviewMouseDoubleClick Yes No
PreviewMouseDown Yes No
PreviewMouseLeftButtonDown Yes No
PreviewMouseLeftButtonUp Yes No
PreviewMouseMove Yes No
PreviewMouseRightButtonDown Yes No
PreviewMouseRightButtonUp Yes No

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PreviewMouseUp Yes No
PreviewMouseWheel Yes No

The mouse events use several delegates for mouse handling. For those events reacting to a
mouse button the following delegate is used:

C#

public delegate void MouseButtonEventHandler(
Object sender,
MouseButtonEventArgs e
)

VISUAL BASIC

Public Delegate Sub MouseButtonEventHandler ( _
sender As Object, _
e As MouseButtonEventArgs _
)

For those events reacting to other mouse events, such as moving, the following delegate is used:

C#

public delegate void MouseEventHandler(
Object sender,
MouseEventArgs e
)

VISUAL BASIC

Public Delegate Sub MouseEventHandler ( _
sender As Object, _
e As MouseEventArgs _
)

The last event handler delegate is only used within WPF and handles mouse wheel events:

C#

public delegate void MouseWheelEventHandler(
Object sender,
MouseWheelEventArgs e
)

VISUAL BASIC

Public Delegate Sub MouseWheelEventHandler ( _
sender As Object, _
e As MouseWheelEventArgs _

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)

However, as in the Keyboard event handler, the two Mouse EventArgs classes are implemented
differently in Silverlight than in WPF.

The MouseEventArgs implementation:

Property / Method WPF Silverlight
GetPosition(IInputElement) Yes Yes
LeftButton Yes No
MiddleButton Yes No
MouseDevice Yes No
RightButton Yes No
StylusDevice Yes Yes
XButton1 Yes No
XButton2 Yes No

The MouseButtonEventArgs class adds some additional properties to the MouseEventArgs class.
The additional implementation details are:

Property / Method WPF Silverlight
ButtonState Yes No
ChangedButton Yes No
ClickCount Yes No

There is no difference between MouseEventArgs and MouseButtonEventArgs within the current
release of Silverlight 2. However, due to the separation of the two classes in Silverlight, the
assumption that future support for the additional MouseButtonEventArgs properties is likely
true.

In order to obtain right mouse button and wheel support in Silverlight, developers need to
interact with the browser through JavaScript and pass the mouse data back to Silverlight. Since
Silverlight is, at its core, a browser plug-in, it is reliant on the plug-in models of the browser.
Most browsers have special handling for the right mouse click and wheel events, and therefore
pose a problem for the Silverlight plug-in. However, there are several implementations solving
this issue available on the web through the use of browser inter-operation capabilities.

IsEnabled
WPF’s UIElement base class implements the IInputElement interface, in which the Boolean
property IsEnabled is defined. By setting this property, a developer can control whether all the
nested children are enabled or not.

In Silverlight, however, this interface is not implemented by UIElement, and the bubbling
functionality of IsEnabled is lost. Possible workarounds are either the brute force method of
setting each nested control independently or binding the IsEnabled property to a global setting.

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Local File Access
WPF applications have a full range of capabilities in accessing local file resources depending
upon the requirements of the application. Silverlight, on the other hand, has very limited access
to local resources. Currently, Silverlight needs to acquire permission from the user via the
OpenFileDialog to obtain Read access to a local file resource. Silverlight can only write data to
isolated storage, but this is subject to change in later implementations of Silverlight.

OpenFileDialog
From a user-interface point of view, the OpenFileDialog in both WPF and Silverlight are virtually
identical. Both implementations allow for multiple files to be selected.

The major difference between the two implementations is the handling of the selected file. In
WPF, the file can be returned to the application as a path and the application can open it as it
needs to (for writing or reading). In Silverlight file is returned to the application as a FileInfo
object. The name of the file is known, but none of the path information is available. In addition,
the Silverlight application can only obtain a read-only stream to the file (direct access to the file
system is forbidden).

A minor difference between the two implementations is the setting of the dialog’s title. WPF
allows the application to set a title to the dialog window, while Silverlight does not.

SaveFileDialog
The SaveFileDialog allows an application to let the user decide where to store data. WPF can
store information to the user’s system without any user interaction as well.

The current implementation of Silverlight does not contain a SaveFileDialog class. The only
method to persist data through sessions would be to use local IsolatedStorage. Unfortunately,
this method would prevent the user from accessing the data outside the Silverlight application.

Silverlight 3 Note
The future release of Silverlight 3 will include an implementation for storing data on the local file system
with the user’s permission through the use the SaveFileDialog.

Sub-Pixel Rendering
WPF uses a technology called Pixel Snapping to reduce anti-aliasing effects on UI elements.
Silverlight uses Layout Rounding to achieve a similar effect.

To turn Pixel Snapping on in WPF (pixel snapping is off by default) set the SnapsToDevicePixels
property to true.

<Rectangle x:Name="MyShape" SnapsToDevicePixels="True" … />

Or in code:

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C#

this.MyShape.SnapsToDevicePixels = true;

VISUAL BASIC

Me.MyShape.SnapsToDevicePixels = True

In Silverlight, the UseLayoutRounding property is set to true by default. To turn on sub-pixel
rendering, set this property to false.

<Rectangle x:Name="MyShape" UseLayoutRounding="False" … />

Or in code:

C#

this.MyShape.UseLayoutRounding = false;

VISUAL BASIC

Me.MyShape.UseLayoutRounding = False

Font Support
As expected, WPF supports all the fonts installed in the Windows operating system. Silverlight,
however, natively supports only a handful of fonts. Additional fonts must be embedded within a
Silverlight application in order to use them, or dynamically downloaded as needed (see FONTS
later in this paper for how to do this).

Supported local fonts for text elements in Silverlight are:
Arial
Arial Black
Comic Sans MS
Courier New
Georgia
Lucinda Grande / Lucida Sans Unicode
Times New Roman
Trebuchet MS
Verdana
Silverlight contains a fallback font called “Portable User Interface.” This is the font used if none
is specified. However, it is merely an alias to the Lucinda Grande / Lucida Sans font face on
Windows platforms; it may be different on other operating systems. According to Microsoft

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documentation, Lucinda Grande and Lucinda Sans are aliases for the same font and usually
named together for compatibility reasons.

Finally, there are several East Asian fonts that can be used if available on the local computer as
well as additional ones if the local computer is running Windows or the Mac OS.

Adding additional fonts in Silverlight is a simple as creating adding the required fonts either as
TrueType (ttf) files or compressed into a Zip archive as Content Items to the project. Setting the
FontSource of a TextBlock control to the resource containing desired fonts will set the
appropriate font. The font can then be used as follows, where “Custom Font” is the name of a
font stored in the CustomFont.ttf file:

<TextBlock FontFamily="customfont.ttf#Custom Font">
Written in my Custom Font.
</TextBlock>

And from a zip archive:

<TextBlock FontFamily="customfont.zip#Custom Font">
</TextBlock>

In WPF fonts can be added as Content Items to the application, and are separate from the
applications binary assemblies. To insure that the fonts are available to the application upon
deployment, the CopyToOutputDirectory element should be set to “PreserveNewest.”

Additionally, fonts can be added to a WPF application as Resource Items. The following XAML
example shows how to reference a font resource:

<TextBlock FontFamily="./resources/#Custom Font">
</TextBlock>

Graphics
Both Silverlight and WPF support vector-based drawing elements as well as support for raster
images in a variety of formats.

Most graphical functions in WPF are accelerated by offloading the graphics workload to the
GPU. Silverlight, however, cannot hand off this processing to the graphics card, and therefore
most perform all calculations in software.

Silverlight 3 Note
Silverlight 3 will support some hardware acceleration through two new parameters on the Silverlight plug-
in, EnableGPUAcceleration and EnableCacheVisualization. Additionally, an entire panel can be cached and
rendered by the GPU through the use of the new CacheMode property.

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2D Graphics

Bitmap Effects
Bitmap effects are simple pixel processing operations performed on WPF content. Since the
bitmap effect occurs replaces the Visual object’s built-in rendering, bitmap effects are rendered
in software instead of accelerated through hardware.

There are five built-in bitmap effects implemented within WPF.

In addition to the default Bitmap Effects, WPF allows the creation of custom effects. However,
creating custom effects entails writing an unmanaged COM library containing the effects and a
managed-code wrapper for integration into WPF.

Silverlight does not support bitmap effects. In some cases, such as adding drop shadows, there
are ways to work around the limitation by using duplicate elements and offsetting them from
one another. For the more visually complex effects, such as blurring, there are no easy methods
for recreating the effect.

Silverlight 3 Note
The future release of Silverlight 3 will include a form of bitmap effects called pixel-shader effects. The
pixel-shader mechanism will perform many of the same effects previously unavailable to Silverlight
applications, including writing custom pixel-shaders.

Important Note:
BitmapEffects are actively being discouraged by Microsoft and are being deprecated. Instead,
the recommended approach is to use Effects; however, only blur and drop shadow effects have
been created. Effects, not coincidentally, are written with the same pixel-shading technology
that will be available to Silverlight 3; so shaders written today will be usable with Silverlight 3.

Brushes
Everything drawn on a WPF or Silverlight surface is visible due to brushes. Brushes draw
everything from lines to backgrounds to text. Brushes come in several types and allow for great
flexibility in their implementation.

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There are a variety of brushes available to both Silverlight and WPF.

Brush WPF Silverlight
SolidColorBrush Yes Yes
LinearGradientBrush Yes Yes
RadialGradientBrush Yes Yes
ImageBrush Yes Yes
DrawingBrush Yes No
VisualBrush Yes No
TileBrush Yes No
VideoBrush No Yes

The lack of a TileBrush in Silverlight prevents both the Video and Image brushes from also being
tiled.

Kiosks
Kiosks are typically defined as stand-alone devices with a complete user interface. Users are not
allowed to access anything other than the kiosk application.

WPF Kiosk
To create a WPF kiosk, the application should be set to fill the entire screen and prevent the
user from minimizing or otherwise interacting with any other part of the system.

To force the application’s main window into a maximized, borderless form, the following XAML
can be used:

<Window x:Class="TestWPF.Window1"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Kiosk"
WindowStyle="None"
WindowState="Maximized"
Topmost="True">



</Window>

Additionally, the developers could trap certain key-strokes to prevent users from circumventing
the application and accessing other system resources.

Silverlight Kiosk
Kiosks in Silverlight act slightly differently, because Silverlight applications cannot set the full-
screen mode during instantiation or in the page’s Loaded event handler. Instead, full –screen
mode can only be entered upon response of a user-initiated event such as a key-press.

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The following code will switch from full-screen to normal mode when the user presses the
Escape key (assuming the handler is attached to the page’s KeyDown event):

C#

void Page_KeyDown(object sender, KeyEventArgs e)
{
if (e.Key == Key.Escape)
App.Current.Host.Content.IsFullScreen =
!App.Current.Host.Content.IsFullScreen;
}

VISUAL BASIC

Private Sub Page_KeyDown(ByVal sender As Object, ByVal e As KeyEventArgs)
If e.Key = Key.Escape Then
App.Current.Host.Content.IsFullScreen = _
Not App.Current.Host.Content.IsFullScreen
End If
End Sub

Note, full-screen mode for Silverlight only forces the Silverlight application into full screen; any
surrounding HTML is lost in full-screen mode.

In addition, Silverlight also limits keyboard entry to the following keys: ESCAPE, UP, DOWN,
LEFT, RIGHT, PAGE UP, PAGE DOWN, HOME, END, SPACEBAR, TAB, and ENTER. This limitation is
by design so that a malicious web site is prevented from mimicking the system’s operating
system to trick the user.

Object Trees

Visual Base Class
The Visual base class is the class that all WPF visually rendering elements eventually derive from.
It supports functionality such as printing and encoding the visual to a bitmap image. The Visual
base class itself derives from DependencyObject.

Silverlight does not implement the Visual base class. Instead Silverlight UI elements have
several different class hierarchy structures. Controls, such as TextBox and Button, derive from
the Control base class, FrameworkElement, UIElement and then from DependencyObject.
Other UI Elements, such as Panel or TextBlock, do not inherit from the Control base class, but
still have FrameworkElement and UIElement in their base class hierarchy. Note that this list is
not the absolute hierarchy for all controls, just some common base classes that developers can
rely upon existing somewhere in the chain of base classes.

Even though Silverlight and WPF UI elements ultimately derive from DependencyObject, the
class has little to do with UI rendering. Instead the DependencyObject class allows objects to
participate in the dependency property system. DependencyObject classes are not necessarily
visual elements.

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This difference makes writing a shared code base difficult at best since the lowest common UI-
related base classes are not compatible programmatically.

VisualTreeHelper
The VisualTreeHelper class allows the developer to examine and work with the visual tree
structure. The implementation of this helper class works around the limitation of Silverlight not
having a Visual base class.

Both WPF and Silverlight contain this helper class; however, they are implemented differently.

Method WPF Silverlight
FindElementsInHostCoordinates No Yes
GetBitmapEffect Yes No
GetBitmapEffectInput Yes No
GetChild Yes Yes
GetChildrenCount Yes Yes
GetClip Yes No
GetContentBounds Yes No
GetDesecendantBounds Yes No
GetDrawing Yes No
GetEdgeMode Yes No
GetEffect Yes No
GetOffset Yes No
GetOpacity Yes No
GetOpacityMask Yes No
GetParent Yes Yes
GetTransform Yes No
GetXSnappingGuidelines Yes No
GetYSnappingGuidelines Yes No
HitTest Yes No

The Silverlight method, FindElementsInHostCoordinates, and the WPF method, HitTest, have
similar purposes: to find UI elements that touch a specific point. One difference between the
two methods is that Silverlight hit tests are performed using the global coordinate system, while
WPF uses the local coordinate system of the specified UI element.

To iterate over all the elements under the mouse pointer in a Silverlight application, the
following code snippet could be used as a starting point:

C#

void Page_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
IEnumerable<UIElement> elements;

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elements =
VisualTreeHelper.FindElementsInHostCoordinates(e.GetPosition(null), this);

foreach(UIElement item in elements)
{
// do something.
}
}

VISUAL BASIC

Private Sub Page_MouseLeftButtonDown(ByVal sender As Object, _
ByVal e As MouseButtonEventArgs)

Dim elements As IEnumerable(Of UIElement)

elements = _
VisualTreeHelper.FindElementsInHostCoordinates(e.GetPosition(Nothing), Me)

For Each item As UIElement In elements
' do something.
Next

End Sub

The three shared methods allow developers to query the visual tree for a particular UI element
and retrieve its children or parent.

CONTROL LIBRARY
The following table outlines the various controls provided to WPF and Silverlight, as well as the
location where they can be downloaded if not part of the default installation.

Table taken from http://msdn.microsoft.com/en-us/library/cc903925(VS.95).aspx).

In the case of Silverlight, some controls are available outside the default installation; such as
from the Silverlight Toolkit (Toolkit) available at http://www.codeplex.com/silverlight, or the
Silverlight SDK (SDK). The Silverlight Toolkit is updated regularly, so checking the web site on a
periodic basis is recommended.

Control WPF Silverlight
AccessText Yes No
AdornedElementPlaceholder Yes No
AdornerDecorator Yes No
AutoCompleteBox No Toolkit
Border Yes Yes
BulletChrome Yes No
BulletDecorator Yes No
Button Yes Yes

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ButtonChrome Yes No
Calendar Yes SDK
Canvas Yes Yes
CheckBox Yes Yes
ClassicBorderDecorator Yes No
ComboBox Yes Yes
ComboBoxItem Yes Yes
ContentControl Yes Yes
ContentPresenter Yes Yes
ContextMenu Yes No
Control Yes SDK
DataGrid Yes SDK
DatePicker Yes SDK
Decorator Yes No
DockPanel Yes Toolkit
DocumentPageView Yes No
DocumentReference Yes No
DocumentViewer Yes No
Ellipse Yes SDK
Expander Yes Toolkit
FixedPage Yes No
FlowDocumentPageViewer Yes No
FlowDocumentReader Yes No
FlowDocumentScrollViewer Yes No
Frame Yes No
FrameworkElement Yes No
Glyphs Yes No
Grid Yes Yes
GridSplitter Yes SDK
GridViewColumnHeader Yes No
GridViewHeaderRowPresenter Yes No
GridViewRowPresenter Yes No
GroupBox Yes No
GroupItem Yes No
HeaderedContentControl Yes Toolkit
HeaderedItemsControl Yes Toolkit
HyperlinkButton No Yes
Image Yes Yes
ImplicitStyleManager Yes Toolkit
InkCanvas Yes No
InkPresenter Yes Yes
ItemsControl Yes Yes
ItemsPresenter Yes Yes
Label Yes Toolkit
Line Yes Yes
ListBox Yes Yes

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ListBoxChrome Yes No
ListBoxItem Yes No
ListView Yes No
ListViewItem Yes No
MediaElement Yes Yes
Menu Yes No
MenuItem Yes No
MultiScaleImage No Yes
NavagationWindow Yes No
NumericUpDown No Toolkit
Page Yes No
PageContent Yes No
PageFunction Yes No
PasswordBox Yes Yes
Path Yes Yes
Polygon Yes Yes
Polyline Yes Yes
Popup Yes Yes
ProgressBar Yes Yes
RadioButton Yes Yes
Rectangle Yes Yes
RepeatButton Yes Yes
ResizeGrip Yes No
Ribbon Yes No
RibbonWindow Yes No
RichTextBox Yes No
ScrollBar Yes Yes
ScrollChrome Yes No
ScrollContentPresenter Yes Yes
ScrollViewer Yes Yes
Separator Yes No
Slider Yes Yes
StackPanel Yes Yes
StatusBar Yes No
StatusBarItem Yes No
SystemDropShadowChrome Yes No
TabControl Yes SDK
TabItem Yes SDK
TabPanel Yes No
TextBlock Yes Yes
TextBox Yes Yes
Thumb Yes Yes
TickBar Yes No
ToggleButton Yes Yes
ToolBar Yes No
ToolBarOverflowPanel Yes No

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ToolBarPanel Yes No
ToolBarTray Yes No
ToolTip Yes Yes
Track Yes No
TreeView Yes Toolkit
TreeViewItem Yes Toolkit
UniformGrid Yes No
UserControl Yes Yes
ViewBox Yes Toolkit
Viewport3D Yes No
VirtualizingStackPanel Yes No
WebBrowser Yes No
Window Yes No
WindowsFormsHost Yes No
WrapPanel Yes Toolkit

Note, that even when Silverlight and WPF share a control, they may be implemented differently.
For example, in WPF, a Canvas object contain Left, Right, Top, and Bottom dependency
properties. In Silverlight, the Canvas object only exposes the Left and Top dependency
properties. The Left and Top properties take precedent over the Right and Bottom properties,
but worth noting if porting positioning logic from WPF to Silverlight.

GENERAL

Routed Events
There are three types of routed events: direct, bubbling and tunneling. Direct events are those
events that are only handled by the element creating the event. Bubbling events are those
events that travel upward through the visual tree and can be handled by any parent of the
source element. Finally, tunneling events are those events that travel downward through the
visual tree and can be handled by any child of the source element.

WPF supports all three types of routed events, while Silverlight only supports direct and
bubbling events.

Additionally, WPF supports the creation of custom routed events via the EventManager helper
class. Silverlight currently does not support custom routed events.

Data-Binding
Data-binding is WPF’s and Silverlight’s mechanism of associating data to controls. Changes to
the source data are propagated to the associated controls according to the binding rules set on
them. Data can be bound to just about any property on any UI element.

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The following snippet of XAML is a simple example of data binding.

<TextBlock Text="{Binding Person, Path=FirstName}" />

Binding Modes
There are four binding mode available in WPF: One-Way, Two-Way, One-Time, and One-Way To
Source.
 One-Way binding causes data to flow from the data source to the target element. Changes
to the data source will update the target.
 Two-Way binding causes data to flow from the data source to the target element, and from
the target element back to the data source. Changes to the data source are reflected in the
target element, and updates to the target element are propagated back to the data source.
 One-Time binding cause data to flow from the data source to the target element. However,
the binding does not listen to change notifications, and any changes in the data are not
updated in the target element.
 One-Way To Source binding causes data to flow from the target element to the data source.
Changes in the data source are not propagated to the target element, but changes in the
target element are flowed back to the data source.

Silverlight does not support the One-Way To Source binding mode.

Additionally, the default binding mode, if none is explicitly set, is different between the two
platforms. WPF’s default binding mode is dependent upon the dependency property, while
Silverlight’s default mode is always OneWay.

UpdateSourceTrigger
The UpdateSourceTrigger property of the data binding allows the developer to control when the
data binding occurs. There are three types of UpdateSourceTriggers:
 LostFocus causes the data-binding when the target element loses focus. For example,
tabbing out of a TextBox will cause the data-binding to occur.
 PropertyChanged causes the data-binding to occur whenever the data changes. For
example, typing each key in TextBox will cause the binding to occur.
 Explicit trigger will only cause the binding to occur when the UpdateSource method is called
on the binding.

Silverlight does not support Explicit data-binding. In order to force a data-binding refresh, the
property changed event must be fired in the data source, or the UI element must be forced to
lose focus.

Multi Binding
Data binding maps a single data element to a single property of a UI element. MultiBinding
allows binding multiple data elements to a single property of a UI element. MultiBinding, unlike

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regular binding, requires the use of a ValueConverter, or more specifically, a
MultiValueConverter.

To demonstrate the MultiValueConverter, a simple, contrived, example is needed. The XAML
below declares a TextBlock with a MultiValueConverter and two bindings:

<TextBlock>
<TextBlock.Text>
<MultiBinding Converter="{StaticResource NameConverter}">
<Binding Source="{StaticResource Person}" Path="FirstName" />
<Binding Source="{StaticResource Person}" Path="LastName" />
</MultiBinding>
</TextBlock.Text>
</TextBlock>

And the corresponding MultiValueConverter:

C#

public class NameConverter : IMultiValueConverter
{
public object Convert(object[] values, Type targetType, object parameter,
CultureInfo culture)
{
// Assuming first and last names are passed in.
return string.Concat(values[0], " ", values[1]);
}

// ConvertBack method snipped for brevity.
…
}

VISUAL BASIC

Public Class NameConverter
Implements IMultiValueConverter

Public Function Convert(ByVal values() As Object, _
ByVal targetType As System.Type, _
ByVal parameter As Object, _
ByVal culture As System.Globalization.CultureInfo) As Object _
Implements System.Windows.Data.IMultiValueConverter.Convert

' Assuming first and last names are passed in.
Return String.Concat(values(0), " ", values(1))

End Function

' ConvertBack method snipped for brevity.
…
End Class

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It would be remiss not to mention a simpler solution to this problem in WPF. With Service Pack
1 of WPF 3.5, the StringFormat property has been added to bindings. The above XAML could be
rewritten, without the use of a MultiValueConverter, as:

<TextBlock>
<TextBlock.Text>
<MultiBinding StringFormat="{}{0} {1}">
<Binding Source="{StaticResource Person}" Path="FirstName" />
<Binding Source="{StaticResource Person}" Path="LastName" />
</MultiBinding>
</TextBlock.Text>
</TextBlock>

WPF supports multiple data-binding while Silverlight only allows binding to single value.
However, a viable work-around in Silverlight would be to create a custom class to aggregate the
multiple data elements into a single property and either parse them in the Value Converter or
use the composite value directly.

For example,

C#

public class Person : INotifyPropertyChanged
{
private string _firstName;
private string _lastName;

public event PropertyChangedEventHandler PropertyChanged;

public string FirstName
{
get { return _firstName; }
set
{
_firstName = value;
NotifyPropertyChanged("FirstName");
NotifyPropertyChanged("FullName");
}
}

public string LastName
{
get { return _lastName; }
set
{
_lastName = value;
NotifyPropertyChanged("LastName");
NotifyPropertyChanged("FullName");
}
}

public string FullName
{

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get { return _firstName + " " + _lastName; }
}

private void NotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
try
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
catch (Exception ex)
{
// Error handing snipped.
}
}
}
}

VISUAL BASIC

Public Class Person
Implements INotifyPropertyChanged

Private _firstName As String
Private _lastName As String

Public Event PropertyChanged As PropertyChangedEventHandler _
Implements INotifyPropertyChanged.PropertyChanged

Public Property FirstName() As String
Get
Return _firstName
End Get
_firstName = value
NotifyPropertyChanged("FirstName")
NotifyPropertyChanged("FullName")
End Set
End Property

Public Property LastName() As String
Get
Return _lastName
End Get
_lastName = value
NotifyPropertyChanged("LastName")
NotifyPropertyChanged("FullName")
End Set
End Property

Public ReadOnly Property FullName() As String
Get
Return _firstName & " " & _lastName

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End Get
End Property

Private Sub NotifyPropertyChanged(ByVal propertyName As String)
Try
RaiseEvent PropertyChanged(Me, _
New PropertyChangedEventArgs(propertyName))

Catch ex As Exception
' Omitting error handling for brevity.
End Try
End Sub
End Class

By binding on FullName, Silverlight will receive a change notification whenever either the
FirstName or LastName properties change.

Element Binding
WPF supports binding to other elements within the visual tree. The following is perfectly legal in
a WPF application:

<TextBox x:Name="Field1" />
<TextBlock Text="{Binding ElementName=Field1, Path=Text}" />

Silverlight 3 Note
Element-to-element binding will be supported in Silverlight 3.

Data Providers
While the source object can be any .Net object, WPF provides some specialized data providers
to enhancing the binding experience. The XmlDataProvider and the ObjectDataProvider are two
such data providers. Silverlight, on the other hand, does not provide an implementation of the
ObjectDataProvider.

However, since the source object can be any .Net object, programming around the deficiency is
not difficult in Silverlight. The lost functionality, such as binding to a method, can be achieved
by wrapping the method in a property and implementing the INotifyPropertyChanged interface
judiciously.

Networking

Communications
Silverlight does not have the capability of making a synchronous networking request due to the
potential of blocking the main UI thread. Silverlight can only make asynchronous network calls.

WPF has access to the complete networking stack within the .Net Framework and does not
have this restriction.

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In addition to HTTP communications, Silverlight also can communicate to network resources via
socket programming. Socket development provides interfaces for developers who require a
more tightly controlled access to the network.

HTTP Communications
Support for HTTP communication opens the door to several options within Silverlight; web
services, WCF Services, and REST. Note that Silverlight is still bound to the supported bindings
listed below in the BINDINGS section.

SOAP
Silverlight supports SOAP 1.1 over HTTP, and does not support other versions of SOAP, or other
web services not compliant with WS-I Basic Profile 1.0.

Silverlight only supports textual XML encoding, but not binary encoding.

Silverlight 3 Note
Silverlight 3 will support binary encoding

WPF can support all SOAP versions and multiple encoding types.

Fault Handling
Silverlight cannot currently natively handle SOAP Fault Exceptions due to web browser
limitations. When a fault does occur, an exception is thrown, but does not specify any detail
about the fault. In essence, Silverlight can determine a fault happened, but not why it
happened.

Silverlight 3 Note
Silverlight 3 will implement a solution to provide more detailed information about SOAP exceptions.

Concurrent Connections
Silverlight is bound to the browsers networking stack and is limited to its concurrent connection
settings. The most restrictive of these limits is two concurrent connections, but is dependent on
the system’s maximum network connections. This setting can be changed in the registry under
the following key:
HKEY_LOCAL_MACHINE/ (or HKEY_CURRENT_USER)
SOFTWARE/
Microsoft/
Internet Explorer/
MAIN/
FeatureControl/
FEATURE_MAXCONNECTIONSPERSERVER

WPF has no such restriction and is free to open as many concurrent connections as needed
within system limitations.

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Bindings
Network bindings define the methodology an application uses to connect to network resources.

The System.ServiceModel namespace contains several different types of network bindings.

Binding Class WPF Silverlight
BasicHttpBinding Yes Yes
BasicHttpContextBinding Yes No
NetMsmqBinding Yes No
NetNamedPipeBinding Yes No
NetPeerTcpBinding Yes No
NetTcpBinding Yes No
NetTcpContextBinding Yes No
PollingDuplexHttpBinding Yes Yes
WebHttpBinding Yes No
WS2007FederationHttpBinding Yes No
WS2007HttpBinding Yes No
WSDualHttpBinding Yes No
WSFederationHttpBinding Yes No
WSHttpBinding Yes No
WSHttpContextBinding Yes No

BasicHttpBinding uses HTTP as the transport for communicating through Windows
Communication Foundation (WCF) endpoints to access ASMX-based Web services or other
services conforming to the WS-I Basic Profile 1.1.

PollingDuplexHttpBinding is similar to BasicHttpBinding, except that the WCF services are
configured for duplex communication with a polling client.

Local Isolated Storage
There are some significant changes in the implementation of local isolated storage between
Silverlight and WPF. There are two classes shared between WPF and Silverlight involving
isolated storage: IsolatedStorageFile and IsolatedStorageFileStream. Both classes have
significantly different implementations, and in addition, the Silverlight implementation marks
most of the methods as SecuritySafeCritical or SecurityCritical.

Silverlight also implements the concept of a quota, prohibiting Silverlight applications from
consuming excessive amounts of physical disk space. By default, a Silverlight application is
allowed to consume up to 1 MB of storage. Applications may increase their quota after
receiving approval from the user.

ISOLATEDSTORAGEFILE
Close() Yes Yes
CreateDirectory() Yes Yes

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CreateFile() No Yes
DeleteDirectory() Yes Yes
DeleteFile() Yes Yes
Dispose() Yes Yes
FileExists() No Yes
GetDirectoryNames() Yes Yes
GetFileNames() Yes Yes
GetMachineStoreForApplication() Yes No
GetMachineStoreForAssembly() Yes No
GetMachineStoreForDomain() Yes No
GetStore() Yes No
GetUserStoreForApplication() Yes Yes
GetUserStoreForAssembly() Yes No
GetUserStoreForDomain() Yes No
GetUserStoreForSite() No Yes
IncreaseQuotaTo No Yes
OpenFile() No Yes
Remove() Yes Yes
Property
AvailableFreeSpace No Yes
CurrentSize Yes No
MaximumSize Yes No
Quota No Yes

ISOLATEDSTORAGEFILESTREAM
BeginRead() Yes Yes
BeginWrite() Yes Yes
EndRead() Yes Yes
EndWrite() Yes Yes
Flush() Yes Yes
Read() Yes Yes
ReadByte() Yes Yes
Seek() Yes Yes
SetLength() Yes Yes
Write() Yes Yes
WriteByte() Yes Yes
Property
CanRead Yes Yes
CanSeek Yes Yes
CanWrite Yes Yes
IsAsync Yes No
Length Yes Yes
Position Yes Yes
SafeFileHandle Yes No

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While virtually identical classes, there are significant differences in the constructors for
IsolatedStorageFileStream between the two platforms. WPF provides for eight overloaded
constructors, while Silverlight supports only three of those.

Constructor Silverlight
IsolatedStorageFileStream(String, FileMode) No

IsolatedStorageFileStream(String, FileMode, FileAccess) No

IsolatedStorageFileStream(String, FileMode, IsolatedStorageFile) Yes

IsolatedStorageFileStream(String, FileMode, FileAccess, FileShare) No

IsolatedStorageFileStream(String, FileMode, FileAccess, IsolatedStorageFile) Yes

IsolatedStorageFileStream(String, FileMode, FileAccess, FileShare, Int32) No
IsolatedStorageFileStream(String, FileMode, FileAccess, FileShare,
Yes
IsolatedStorageFile)
IsolatedStorageFileStream(String, FileMode, FileAccess, FileShare, Int32,
No
IsolatedStorageFile)

Resource Dictionaries
Both Silverlight and WPF support resource dictionaries. Resource dictionaries can exist in
multiple places throughout the application; from the application itself to individual controls.

Resources in WPF can be either static or dynamic. Dynamic resources are not available in
Silverlight. Dynamic resources are resources that are evaluated each time they are accessed and
are discussed in the WPF-only implementation section.

Referencing resources from code also differs slightly between Silverlight and WPF. In both
platforms, the resource can be retrieved by its key from the appropriate resource dictionary
(either the immediate resource dictionary or the application resource dictionary).

WPF, however, also supports the FindResource() method to search for a resource key wherever
it may exist. In addition, the WPF implementation supports IEnumerable to allow iterating over
the collection of resources.

Merged Dictionaries

WPF supports external resource files and the ability to merge them into one cohesive resource
dictionary.

<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="MyResources1.xaml" />
<ResourceDictionary Source="MyResources2.xaml" />

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</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>

Silverlight, unfortunately, does not currently support merged resource dictionaries. However, it
is possible to craft a similar solution to dynamically populate the application resource collection
at runtime.

Silverlight 3 Note
The next version of Silverlight will support merged dictionaries in the same way WPF currently does.

Other Differences
In WPF, the FrameworkTemplate base class used for templating, contains a Resources collection
property. Silverlight’s implementation of the FrameworkTemplate class does not have a
Resources property.

Silverlight does not support x:Shared or x:Static attributes. In addition, Silverlight has a smaller
range of shareable types than WPF. Shareable objects are the only types of objects that can be
stored within a resource dictionary.

Custom Dependency Properties

Coerce-value Callback
Silverlight does not support WPF’s implementation of coerce-value callbacks and
DependencyObject.CoerceValue. However, since Silverlight supports property-changed
callbacks, most of the missing implementation can be added.

Read-Only Properties
Silverlight does not support read-only dependency properties. Unfortunately, there is no fool-
proof method for working around this limitation since any external code can call set the
property through the use of the SetValue method.

Property Metadata
Overriding metadata is not supported in Silverlight; a dependency property’s metadata is set as
initially registered to the owner type and cannot change.

Silverlight only supports the PropertyMetadata class, whereas WPF implements several derived
classes (such as UIPropertyMetadata and FrameworkPropertyMetadata). The
PropertyMetadata class is not sealed, so it is possible to derive from it to implement any missing
functionality.

Once constructed, Silverlight’s PropertyMetadata is not as useful as the version implemented in
WPF due to a lack of readable properties. Additionally, API functions such as
DependencyProperty.GetMetadata and DependencyObjectType class are simply missing from
Silverlight.

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AddOwner
The AddOwner mechanism is particularly useful in WPF when attempting to change the
PropertyMetadata of a dependency property defined in an existing class. AddOwner allows the
re-registering of a dependency property to a new owner. Silverlight does not support the
AddOwner method on the DependencyObject class.

Commanding
Commanding is an input mechanism introduced in WPF to provide a separation between UI
elements and the actions taken. Silverlight does not support the concept of commanding as
defined in WPF, it only supports the ICommand interface. Some third-party projects, both open
source and off-the-shelf libraries and used the interface to provide rudimentary commanding to
Silverlight.

.NET FRAMEWORK
Silverlight contains a subset of the .Net framework, called CoreCLR, and there are noticeable
differences in implementation of even the most mundane functionality. Producing an
exhaustive list of framework differences would be a daunting task.

Take, for example, the simple String object and the Split() method.

String.Split() Overloads WPF Silverlight
Split(params char[] separator) Yes Yes
Split(char[] separator, int count) Yes No
Split(char[] separator, StringSplitOptions options); Yes Yes
Split(string[] separator, StringSplitOptions options); Yes Yes
Split(char[] separator, int count, StringSplitOptions options); Yes No
Split(string[] separator, int count, StringSplitOptions Yes No
options);

Silverlight only supports half the overloaded methods as WPF. These types of differences can be
found throughout the entire .Net Framework.

Collections
Looking at the System.Collections and System.Collections.Generic namespaces, several
differences between the implementations of both platforms become apparent.

SYSTEM.COLLECTIONS
Classes WPF Silverlight
ArrayList Yes No
BitArray Yes Yes
HashTable Yes No

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Queue Yes No
SortedList Yes No
Stack Yes No

Typically, this should not be a problem since most of these collections are available in a generic
form. However, use of these classes can be problematic when porting code from WPF to
Silverlight.

SYSTEM.COLLECTIONS.GENERIC
Classes WPF Silverlight
Dictionary<TKey, TValue> Yes Yes
KeyedByTypeCollection<TItem> Yes Yes
HashSet<T> Yes No
LinkedList<T> Yes Yes
List<T> Yes Yes
Queue<T> Yes Yes
SortedDictionary<TKey, TValue> Yes No
SortedList<T> Yes No
Stack<T> Yes Yes
SynchronizedCollection<T> Yes No

Unfortunately, Silverlight doesn’t support the highly efficient HashSet<T>; other data structures
would need to be used as Silverlight doesn’t support the HashTable collection either.

The SortedDictionary and SortedList omissions can easily be worked around using LINQ.

C#

var q = from key in MyDictionary.Keys
orderby key ascending
select MyDictionary[key];

VISUAL BASIC

Dim q = From key In MyDictionary.Keys _
Order By key Ascending _
Select MyDictionary(key)

Cryptography
Like most aspects of Silverlight, cryptography support is a subset of the WPF implementation.
Comparing the classes in System.Security.Cryptography namespaces in both platforms would
not be especially helpful (there are 107 classes in the namespace for WPF, and only 20 for
Silverlight).

Silverlight only supports the AES encryption algorithm. WPF supports the full range of
algorithms in the .Net Framework.

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Silverlight supports four hashing algorithms: SHA1, SHA1Managed, SHA256, and
SHA256Managed. WPF supports all the .Net hashing algorithms.

Threading

Interprocess Synchronization
WPF supports several methods for synchronizing threads between processes; such as the
Monitor, Mutex or Semaphore classes. Silverlight, however, only supports the Monitor class for
synchronization.

Locking
WPF implements support for the ReaderWriteLock class, enabling locks on resources to support
single writers and multiple readers. Silverlight supports locking through the Monitor class,
which grants locks to an object for a single thread. The Monitor class can ensure that no other
thread is allowed to access a code section except by that of the lock owner. Though a bit
coarser than the locks available to WPF, the Monitor should prove to be sufficient for most
multi-threaded needs in Silverlight.

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WPF SPECIFIC FUNCTIONALITY
WPF applications are primarily desktop applications running within the confines of a Windows operating
system. As such, WPF applications do not have the restrictions imposed on Silverlight which runs in a
tightly controlled sandbox within the confines of a web browser.

DESKTOP FUNCTIONALITY

Printing
Unlike printing in the WinForms era, printing in WPF is relatively straight-forward. Any visual
element can be printed, but the most likely scenario would be printing an entire Window.

The following snippet will print the contents of a UIElement using the OS printer dialog window.

C#

PrintDialog dialog = new PrintDialog();

if (dialog.ShowDialog() == true)
{
dialog.PrintVisual(this.MyGrid, "My Grid");
}

VISUAL BASIC

Dim dialog As New PrintDialog

If dialog.ShowDialog() = True Then
dialog.PrintVisual(Me.MyGrid, "My Grid")
End If

This basic printing has limitations: if the size of the visual is larger than an actual page, the
content will get clipped.

For more complex printing needs, such as multiple page printing, WPF offers the PrintDocument
method. Instead of printing a Visual element, the PrintDocument accepts a DocumentPaginator
object. The DocumentPaginator is an abstract class, so developers will have to define a class to
perform the more complex functionality of multiple-page printing.

XPS Documents
XML Paper Specification (XPS) documents maintain a consistent appearance across all display
mediums. WPF has full support for creating, viewing and printing XPS documents through the
XpsDocumentWriter and XpsViewer classes in the System.Windows.Xps namespace.

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There are two types of documents, FlowDocument and FixedDocument. FlowDocuments can
adjust its content to make use of the space within the page.

A simple FlowDocument looks like:

<FlowDocument>
<Paragraph>
Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do
eiusmod tempor incididunt ut labore et dolore magna aliqua.
</Paragraph>
<Paragraph>
Sed ut perspiciatis unde omnis iste natus error sit voluptatem
accusantium doloremque laudantium, totam rem aperiam, eaque ipsa
quae ab illo inventore veritatis et quasi architecto beatae vitae
dicta sunt explicabo.
</Paragraph>
</FlowDocument>

A Document consists of two main TextElements, blocks and inlines. WPF implements five types
of block elements:

 Paragraph
Contains a collection inline elements representing the content of a paragraph. By
default, any content placed between the start and end tags automatically become the
content of a Run inline element and added to the Paragraph’s Inline collection.

 Section
Groups block element together without changing the physical structure. This is useful
when multiple blocks share a common look, such as a background color.

 List
Supports creating bulleted, numbered, or plain lists. Contains a collection of ListItem
elements.

 Table
Supports placing elements into columns and rows.

 BlockUIContainer
Holds any UIElelement to allow embedding of virtually any WPF visual element.

Inline elements mirror virtually all the inline elements within HTML: spans, bold, italic,
underline, and hyperlink to name a few.

Displaying Documents
WPF provides three controls for displaying documents.

 FlowDocumentScrollViewer
Displays the document as one continuous block with vertical and/or horizontal scrolling

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available.

 FlowDocumentPageViewer
Shows the document in individual pages and supports zooming.

 FlowDocumentReader
Supports the full-range of viewing capabilities, including zooming, and text searching,
alternating between scrolling and paging.

Annotations
In addition to displaying documents, WPF implements an annotation system for adding textual
notes or highlights to an existing document without changing the original document. The one
downside to the annotating service is that WPF does not expose any user interface for adding
annotations or highlighting; the developer needs to create their own UI and tie it to the
annotation service APIs.

Speech
WPF supports the speech APIs found in the System.Speech namespace, which in turn, are
wrappers around the Microsoft SAPI framework, a Win32 library. However, the speech API is
not actually WPF technology: no dependency properties, routed events, or other aspects that
make WPF what it is. In fact, there is no XAML syntax for speech; instead speech relies on a
different XML dialect called Speech Synthesis Markup Language (SSML).

There are two aspects to the speech APIs: synthesis (speaking text) and recognition (listening to
commands). The System.Speech namespace provides classes for both concepts, but recognition
requires a speech recognition engine to be installed. Fortunately, Windows Vista has one by
default (as well as Office XP or later).

Speech Synthesis
The most important class for converting text to speech is the SpeechSynthesizer class. Here is a
simple example:

C#

SpeechSynthesizer speaker = new SpeechSynthesizer();
speaker.Speak("Text to speech from WPF.");

VISUAL BASIC

Dim speaker As New SpeechSynthesizer
speaker.Speak("Text to speech from WPF.")

Speech Recognition
Speech recognition begins with the SpeechRecognizer class, which exposes the
SpeechRecognized event. Spoken words are converted to text and set as part of the event

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arguments. This method is ideal for converting spoken words into text to be stored in a text
box.

Supporting commands requires more work, such as defining a grammar dictionary in the Speech
Recognition Grammar Specification (SRGS) XML dialect, or by using the SrgsGrammar helper
class. The SrgsGrammar class is not as fully functional as creating a SRGS document.

InterOp
Interoperability in WPF generally refers to interacting with previous technology such as Win32
applications, COM+, and ActiveX controls.

WindowsFormsHost
The WindowsFormsHost control allows a developer to embed a WinForms control directly into a
WPF application with little work. However, the WindowsFormsHost control cannot overlap or
be overlapped by any WPF content. Each region in an application can only be controlled by one
display technology.

Hosting a Windows Forms NumericUpDown control within a WPF application:

<WindowsFormsHost>
<winforms:NumericUpDown x:Name="myUpDownControl" />
</WindowsFormsHost>

ElementHost
ElementHost is the Windows Forms equivalent of WindowsFormsHost, and allows embedding of
WPF elements within a WinForms application. Of course, in WinForms, the work must be done
in code instead of declarative XAML.

ActiveX Controls
Embedding an ActiveX control in a WPF application uses the same methodology as embedding a
Windows Forms control; that is, via the WindowsFormsHost element. However, the reverse,
exposing a WPF control as an ActiveX control is not currently supported.

Advanced InterOp
More complex interoperability may be performed in WPF through the knowledge of window
handles (HWNDs). While most of WPF does not implement any method for interacting with
HWNDs, the HwndHost, a subclass of FrameworkElement, class can host any object exposing an
HWND. In addition, WPF defines an HwndSource to expose any visual element as a HWND for
consumption in a Win32 application.

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XAML
WPF supports some additional XAML elements and attributes than Silverlight. Styles are one
example where WPF adds additional functionality. Note, Microsoft is working to implement
more and more of WPF within the Silverlight platform.

Styles
Styles in WPF are analogous to HTML’s cascading style sheets, in that they allow changing the
appearance of any visual element from a single location; essentially abstracting the look of the
control from its functionality. While both WPF and Silverlight can use styles, WPF implements
additional functionality with regard to styles.

BasedOn Styles
The BasedOn property allows a form of visual inheritance between styles. As the name states, a
developer can base one style off of another.

<Style
x:Key="DefaultText"
TargetType="TextBlock">

<Setter Property="FontFamily" Value="Segoe UI"/>
<Setter Property="FontSize" Value="11" />
<Setter Property="Foreground" Value="Black" />
</Style>

<Style
x:Key="EmphasizedText"
TargetType="TextBlock"
BasedOn="{StaticResource DefaultText}">
<Setter Property="Foreground" Value="Red" />
<Setter Property="FontWeight" Value="Bold" />
</Style>

Silverlight 3 Note
Based-On styles are supported by Silverlight 3, as well as dynamic styles that allow styles to be changed on
elements after they have been set.

Implicit Styles
Implicit styles are styles defined without a key, such as:

<Style TargetType="{x:Type TextBlock}">
<Setter Property="FontFamily" Value="Segoe UI"/>
<Setter Property="FontSize" Value="15" />
<Setter Property="Foreground" Value="Black" />
</Style>

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An implicit style will set the properties of any visual element matching the TargetType. This is
an easy method for updating the look-and-feel of an entire application without having to add
Style declarations to every control.

In some cases, it might be necessary to remove an implicit style on a visual element. To negate
an implicit style, simply set the Style property of the element to {x:Null}.

USER INTERFACE

3D Graphics
WPF supports hardware accelerated 3D functionality within the WPF graphics system. All 3D
content is viewed through a Viewport3D container, and can be completely declared from within
XAML.

WPF supports many 3D features including cameras, models, meshes, materials, lights,
transformations and animation.

Silverlight 3 Note
Silverlight 3 gains some 3D features, such as perspective projections in 3D for scaling and rotational
effects. In addition, Silverlight 3 will support hardware acceleration for many effects for which it previously
used software rendering.

However, it will not support the full range of 3D capabilities found in WPF.

Themes
Themes are a set of visual styles and control templates available to WPF applications and are
not necessarily application-specific. WPF installs several OS-specific themes such as “Windows
Classic,” “Luna”, and “Aero” to name a few. In addition, additional themes may be found for
free and for sale on the internet. One free source can be found at http://wpf.codeplex.com,
containing nine professional themes available in both WPF and Silverlight platforms (separately
through the Silverlight Toolkit).

In practicality, themes are defined as resource dictionaries containing implicit styles and control
templates for as many elements as necessary to define the theme. In most cases, virtually every
visual control would be styled in the theme.

Themes can be created and placed within the themes subfolder off the root of the project.
Theme resource dictionaries also have a distinct naming convention in the form of
ThemeName.ThemeColor.xaml. The fallback theme is always named themesgeneric.xaml.
To add statically add a theme to a project; simply include the following XAML in the application’s
XAML file:

<Application.Resources>

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<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="themescustom.blue.xaml"/>
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</Application.Resources>

Skins
Skins are almost identical to themes, except that skins are geared to a specific application while
themes are system oriented. Different applications can share system-wide themes, while an
individual application may support additional skins.

Applications are usually designed to be skinned by end-users and therefore provide a skinning
API for designers. The only major difference is that skin resource files typically name styles
explicitly, whereas themes normally use implicit naming. However, this is not a hard and fast
rule.

Distinguishing between themes and skins is a nebulous area at best. The current line of thinking
is that themes refer to the look and feel of an application to match the operating system, and
skins refer to changing an applications appearance to suit the user.

Image Manipulation
WPF implements common imaging capabilities found with the Microsoft GDI+ library, as well
overcoming some of the short-comings of that aging library. WPF supports both managed and
unmanaged image manipulation libraries. However, this document will focus on the managed
library found within the Systme.Windows.Media and System.Windows.Media.Imaging
namespaces.

WPF Image Formats
WPF supports the following bitmap (raster) image types:
 BMP
 JPEG
 PNG
 TIFF
 Windows Media Photo
 GIF
 Icon

Both encoders (writers) and decoder (readers) are available for each of the bitmap image types.
The basic building block of WPF imaging is the BitmapSource class. It can represent not only a
single image, but multiple frames in GIF or TIFF images (both formats support multiple frames).

The following snippet shows to save a Visual element, named “MyGrid” in this example, to a
PNG image file sized at 800x600 pixels at the default 96 dots per inch:

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C#

string fileName = "test.png";
RenderTargetBitmap target = new RenderTargetBitmap(800, 600, 96, 96,
PixelFormats.Default);

target.Render(this.MyGrid);
BitmapEncoder encoder = new PngBitmapEncoder();
encoder.Frames.Add(BitmapFrame.Create(target));

// Save image to disk
FileStream fs = File.Open(fileName, FileMode.Create);
encoder.Save(fs);
fs.Close();

VISUAL BASIC

Dim fileName As String = "test.png"
Dim target As New RenderTargetBitmap(800, 600, 96, 96, PixelFormats.Default)

target.Render(Me.MyGrid)
Dim encoder As New PngBitmapEncoder()
encoder.Frames.Add(BitmapFrame.Create(target))

' Save image to disk
Dim fs As FileStream
fs = File.Open(fileName, FileMode.Create)
encoder.Save(fs)
fs.Close()

Silverlight 3 Note
A WriteableBitmap class has been added to Silverlight 3 that implements an API for creating bitmaps
programmatically. With the new SaveFileDialog class, creating and storing images for later retrieval will
now be possible.

Page-Based Navigation
Traditional client development centers on windows and forms and WPF has no issues working in
that paradigm. However, the internet brought the web page, and navigational-based web
applications. WPF attempts to bridge the divide by bringing the page-based navigation
metaphor to the desktop.

Applications using page-based navigation typically start with the NavigationWindow element,
instead of a Window element. Individual screens are defined through the Page element. In
addition, WPF supports a Frame element that may also contain Pages for navigation purposes,
but embedded within a screen instead of being the top-level window.

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The majority of paging interaction occurs through the NavigationService instance exposed by
the Page element, or through a static method on the NavigationService class. The Navigate()
method is overloaded to accept instances of Pages as well as URIs, relative or external.

Silverlight 3 Note
Silverlight 3 will contain a new NavigationFramework that will function similarly to the page-based
navigation implementation in WPF, as well as take advantage of the browser’s Back and Next buttons.

Journal
The journal is an aspect of the page-based navigation system to provide history of pages visited.
NavigationWindows implement a journal by default, while Frames need to request one through
the JournalOwnership property.

Pages can opt out of being stored in the journal by setting the RemoveFromJournal property to
true.

Input Gestures
While the term gestures may suggest some fancy high-tech method for analyzing mouse
movements, the reality is much simpler. Input gestures are a facility for defining a sequence of
key-strokes, such as Alt-C or Ctrl-Alt-F2 or mouse button clicks such as Alt-Left Click.

Input gestures work in conjunction with WPF commands. Commands can be associated with
one or more input gestures.

Input gestures can be declared in XAML as well as in code. For example, to attach the F1 key to
the help command or CTRL-ALT-F2 sequence to a print command, a developer could code in
XAML:

<Window.InputBindings>

<KeyBinding Command="Help" Key="F1" />


<KeyBinding Command="Print" Gesture="Control+Alt+F2" />

</Window.InputBindings>

Mouse gestures are defined in the same manner:
<Window.InputBindings>

<MouseBinding Command="CustomCommand" Gesture="Alt+LeftClick" />

</Window.InputBindings>

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GENERAL FUNCTIONALITY

Freezable Objects
A freezable object in WPF is an object deriving from the Freezable base class. It is special in that
when frozen, the object can no longer be modified. Once frozen, the object can then be shared
across threads and processes; non-frozen objects cannot be shared in this manner.
Brushes, Transforms, and Geometry objects are all freezable objects; in fact the majority of
freezable objects in WPF are contained within the graphics libraries. When frozen, performance
will improve due to the way these objects have been implemented. A large portion of the
graphics sub-system internally implements unmanaged code, requiring the system to monitor
these objects for changes. When frozen, the system no longer needs to monitor the objects for
changes and can make optimizations based on this fact.

Once frozen, a freezable object cannot be unfrozen; however, it can be cloned. In addition, not
all freezable objects can be frozen and therefore the base class exposes a CanFreeze property.

Finally, freezing an object that contains freezable objects will also freeze all the children. For
example, freezing an object deriving from Geometry will also freeze all the Figures and
Segments contained within it.

Data Providers
WPF implements a data provider model for data binding and ships with two concrete data
provider classes: ObjectDataProvider and XmlDataProvider. In addition, it is possible to create
custom data providers by deriving from System.Data.DataSourceProvider.

XmlDataProvider
The XmlDataProvider can provide access to an embedded XML data structure or a complete
XML file. An XML data structure can be embedded into an applications resource dictionary as
follows:

<Window.Resources>
<XmlDataProvider x:Key="MyData" XPath="Teams">
<x:XData>
<Teams xmlns="">
<Team Name="NY Yankees">
<Players>
<Player>
<Name>Derek Jeter</Name>
<Position>Shortstop</Position>
</Player>
<Player>
<Name>Mariano Rivera</Name>
<Position>Closer</Position>
</Player>
</Players>

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</Team>
</Teams>
</x:XData>
</XmlDataProvider>
</Window.Resources>

To load data from an external XML data file,

<Window.Resources>
<XmlDataProvider x:Key="MyData" XPath="Teams" Source="Baseball.xml">
</Window.Resources>

To bind to this Xml snippet, use standard binding syntax with the XPath set appropriately.

<TextBlock
Text="{Binding Source={StaticResource MyData}, XPath=Team/@Name}" />

ObjectDataProvider
The XmlDataProvider may not be suitable for all purposes, especially when data may be already
stored in custom objects. The ObjectDataProvider wraps any .Net object as a data source.
Though most .Net objects can already be set as a data source, the ObjectDataProvider provides
additional functionality; such as exposing methods as a data source, allowing parameterized
construction of the object, and supporting additional asynchronous binding.

<Window.Resources>


<local:BaseballTeams x:Key="Teams" />


<ObjectDataProvider
x:Key="MyData" ObjectType="{x:Type local:BaseballTeams}" />


<ObjectDataProvider
x:Key="Yankees" ObjectType="{x:Type local:BaseballTeams}">
<ObjectDataProvider.ConstructorParameters>
<sys:String>NYY</sys:String>
</ObjectDataProvider.ConstructorParameters>
</ObjectDataProvider>

Validation
WPF provides a framework for adding validation rules to data bindings. The Binding class
contains a collection of ValidationRules in which one or more objects deriving from
ValidationRule can be loaded. Each rule is checked in turn, therefore, all the rules must pass or
the validation fails. Additionally, the validation engine can also be configured to handle
exceptions that may arise in the data source itself by using the ExceptionValidationRule.

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To create a custom validation rule, simply derive from ValidationRule and add any custom logic
to the Validate() method. Then, add the rule to the ValidationRules collection either in code or
declaratively in XAML. For example,

C#

public class EvenValidationRule : ValidationRule
{
public override ValidationResult Validate(object value, CultureInfo
cultureInfo)
{
// Error checking omitted for brevity.
int number = int.Parse(value.ToString());

if (number % 2 != 0)
{
return new ValidationResult(false, "Number must be even.");
}

return new ValidationResult(true, null);
}
}

VISUAL BASIC

Public Class EvenValidationRule
Inherits ValidationRule

Public Overrides Function Validate(ByVal value As Object, _
ByVal cultureInfo As CultureInfo) As ValidationResult

' Error checking omitted for brevity

Dim number As Integer = Integer.Parse(value.ToString())

If number Mod 2 <> 0 Then
Return New ValidationResult(False, "Number must be even.")
End If

Return New ValidationResult(True, Nothing)
End Function
End Class

<TextBox>
<TextBox.Text>
<Binding Source="{StaticResource MyData}" XPath="Team/@Score">
<Binding.ValidationRules>
<local:EvenValidationRule />
</Binding.ValidationRules>
</Binding>
</TextBox.Text>
</TextBox>

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By default, when an element fails its validation, WPF outlines the element with a thin red
border. However, by providing an ErrorTemplate, a designer can change the look-and-feel of
fields failing validation.

The following example shows how to create a validation template and apply it to a TextBox
element.

<ControlTemplate x:Key="TextBoxErrorTemplate">
<DockPanel>
<Border BorderBrush="Red" BorderThickness="0.5">
<Border.BitmapEffect>
<OuterGlowBitmapEffect GlowColor="Red" GlowSize="5"/>
</Border.BitmapEffect>

<AdornedElementPlaceholder x:Name="ph" />
</Border>
<TextBlock
Margin="4,0"
Foreground="Red"
Text="{Binding ElementName=ph,
Path=AdornedElement.(Validation.Errors)[0].ErrorContent}" />
</DockPanel>
</ControlTemplate>

<TextBox Validation.ErrorTemplate="{StaticResource TextBoxErrorTemplate}">
<TextBox.Text>
<Binding Source="{StaticResource MyData}" XPath="Team/@Score">
<Binding.ValidationRules>
<local:EvenValidationRule />
</Binding.ValidationRules>
</Binding>
</TextBox.Text>
</TextBox>

The image below shows the results of this snippet in an error condition, and, as a reference, the
default look is show at the bottom.

Silverlight 3 Note
New features for supporting data validation will be available in Silverlight 3 through the use of built-in
validation controls and an exception system to notify controls of invalid data.

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Dynamic Resources
Dynamic resources differ from static resources in that the framework will evaluate the dynamic
resource every time it is used, whereas a static resource is evaluated once and cached.

The major reason for using dynamic resources is for situations where the value of the resource is
not known until runtime; such as system resources, or other user-settable resources. Other
reasons include situations that require adjusting the contents of a resource during the lifetime
of the application.

Dynamic resources syntax is identical to static resources; other than specifying the
DynamicResource markup extension instead of the StaticResource extension.

For more information on resources, see http://msdn.microsoft.com/en-
us/library/ms750613.aspx.

Code Access Security
WPF supports the .Net Framework’s implementation of code access security (CAS). This security
mechanism limits access to system resources and functions. A full discussion of code access
security is beyond the scope of this paper.

In essence, CAS defines permissions and permission groups that represent a right to access
particular system resources. Code can then request permissions in which it needs to run, what
it would like to have, and what permissions it should never be granted.

All WPF applications, except web browser applications (WBAs), require FullTrust permissions in
order to run. Web browser applications, however, are run with partial trust; typically using one
of the zone-based security sandboxes defined within Internet Explorer (such as the Internet or
Intranet zones).

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SILVERLIGHT SPECIFIC FUNCTIONALITY
Some functionality is available only to the Silverlight platform solely due to the fact that it is a web-
based technology, hosted within a browser.

WEB FUNCTIONALITY

Browser InterOp
A Silverlight application does not necessarily need to consume its entire hosted web page, and
may exist as a smaller region within a rich HTML page. In the case where the Silverlight applet
is a portion of a larger web page, it may become necessary for the applet to communicate with
the page itself.

It is possible for Silverlight to call JavaScript methods, have Javascript call Silverlight methods,
and have Silverlight interact with the HTML document object model (DOM).

To call a JavaScript method from Silverlight:

C#

using System.Windows.Browser;

// call a method
HtmlPage.Window.Eval("customMethod();");

// use invoke syntax
HtmlPage.Window.Invoke("customMethod");

// use invoke syntax with parameters
HtmlPage.Window.Invoke("customMethod", "param1", 12);

// use invoke syntax and get return value.
string name = (string) HtmlPage.Window.Invoke("getName");

VISUAL BASIC

Imports System.Windows.Browser

' call a method
HtmlPage.Window.Eval("customMethod()")

' use invoke syntax
HtmlPage.Window.Invoke("customMethod")

' use invoke syntax with parameters
HtmlPage.Window.Invoke("customMethod()", "param1", 12)

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' use invoke syntax and get return value.
Dim name As String = CType(HtmlPage.Window.Invoke("getName"), String)

To call a Silverlight method from JavaScript, the Silverlight class and name must be attributed
correctly as ScriptableType and ScriptableMember respectively, as follows:

C#

[ScriptableType]
public partial class Page : UserControl
{
public Page()
{
InitializeComponent();
this.Loaded += new System.Windows.RoutedEventHandler(Page_Loaded);
}

void Page_Loaded(object sender, System.Windows.RoutedEventArgs e)
{
HtmlPage.RegisterScriptableObject("SilverlightMethods", this);
}

[ScriptableMember]
public string GetUserName()
{
// assume implementation of UserName property.
return this.UserName;
}
}

VISUAL BASIC

<ScriptableType()> _
Partial Public Class Page
Inherits UserControl

Public Sub New()
InitializeComponent()

AddHandler Me.Loaded, AddressOf Page_Loaded
End Sub

Private Sub Page_Loaded(ByVal sender As Object, ByVal e As EventArgs)
HtmlPage.RegisterScriptableObject("SilverlightMethods", Me)
End Sub

<ScriptableMember()> _
Public Function GetUserName() As String
' assume implementation of UserName property.
Return Me.UserName
End Function
End Class

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Then, within the JavaScript of the hosting page, add the following code:

<script type="text/JavaScript">
function onPluginLoaded()
{
var sl = $get("Xaml1"); // Use ID associated with plugin.
var sm = sl.content.SilverlightMethods;
var name = sm.GetUserName(); // Case sensitive.

// Do something...
}
</script>

All HTML interoperability occurs through the static HtmlPage class; from registering scriptable
methods to interacting with the Html document or window elements.

MEDIA
Silverlight supports rich media services delivered over the web. The Silverlight client supports
several methods of receiving streaming media over the HTTP protocol.

Traditional Streaming
Silverlight can play media streamed to the client using a technique that sends data to the client
at the bit rate of the encoded media, and only sends enough to fill the client buffer. Silverlight’s
default buffer length is 5 seconds. This methodology reduces bandwidth consumption since if
the client is paused or cancelled, the only wasted bandwidth would be from the data stored in
the buffer.

Progressive Download
Silverlight also implements the progressive download delivery method. Unlike smooth-
streaming, the progressive download method streams the entire media file to the client. The
client, however, can begin playing the media without it being completely downloaded. If the
client pauses or cancels the player, the server continues to transmit the entire media file to the
browser’s cache.

Smooth Streaming
Silverlight also supports a relative new adaptive streaming technology dubbed Smooth
Streaming. Smooth Streaming is a hybrid technology, combining traditional streaming with
progressive downloading; transmitting a series of small progressive downloads instead of a
single large one.

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The Smooth Streaming technology is adaptive in that the client can request pieces of data of
various sizes to optimize bandwidth consumption. In addition, the source media can be stored
at different bit rates, and the client can seamlessly choose the best bit rate to use based on any
number of factors, including network conditions and CPU usage.

The major advantages of Smooth Streaming are quick startup, no buffering, and constant
adaptation to the environment. This insures a consistent, and more importantly, a smooth
playback of media.

Timeline Markers
A timeline marker is metadata stored directly within the media file to provide the capability to
skip to specific positions or provide cues for scripting. Within Silverlight, these timeline markers
generate a MarkerReached event within the MediaElement class. The event can be handled in
code to provide any number of enriching experiences, such as media pop-ups.

For example, the following XAML might be used to show media pop-ups as certain markers are
reached within the media stream.

<StackPanel Orientation="Horizontal">
<MediaElement x:Name="movieClip"
Width="640"
Height="480"
MarkerReached="OnMarkerReached"
Source="movieClip.wmv" />

<TextBlock x:Name="popup"
Width="200"
Height="100"
Visibility="Collapsed"
Text="" />
</StackPanel>

The procedural code to display the popup could be implemented as follows:

C#

public void OnMarkerReached(object sender, TimelineMarkerRoutedEventArgs e)
{
popup.Text = e.Marker.Text;
popup.Visibility = Visibility.Visible;
}

VISUAL BASIC

Private Sub OnMarkerReached(ByVal sender As System.Object, _
ByVal e As TimelineMarkerRoutedEventArgs)

Me.popup.Text = e.Marker.Text
Me.popup.Visibility = Visibility.Visible

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End Sub

The code to hide the popup after a set amount of time passes will be left as an exercise to the
reader.

Silverlight’s MediaElement class also populates a Markers collection containing all the timeline
markers appearing in the media file.

DEEP ZOOM
Deep Zoom is a technology for viewing extremely high resolution images through Silverlight.
The technology allows for quicker downloads of a large image by only displaying the portion
being viewed. Deep Zoom also pre-processes an image into many separate resolution images to
allow for speedier zooming and panning.

A separate pre-processing application, the Deep Zoom composer, is used by a designer to
partition an image into a composition of smaller tiles or pieces at a variety of different
resolutions. Deep Zoom calls this an image pyramid.

At run-time the Deep Zoom engine seamlessly stitches the pieces together depending upon how
the image is being viewed.

For example, an image with a resolution of 10,000x10,000 pixels may first be displayed in a
canvas sized at 600x600 pixels. The image downloaded to the browser would not be the entire
image, but a lower resolution version of it. Zooming into the image would cause higher
resolution pieces to be downloaded to the browser, but at no time would the entire
10,000x10,000 image be transferred.

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CODE REUSE STRATEGIES
Sharing code between Silverlight and WPF can be a daunting task, as seen by the myriad differences
between the two platforms. However, with careful planning, developers can share a significant amount
of code between the two technologies. Microsoft is committed to bringing Silverlight and WPF closer
together with each release.

Many of the differences in programming between Silverlight and WPF have been covered in the body of
this whitepaper. However, this section compiles a list of some of the top techniques or strategies you
can use to promote re-use of the code between the two platforms.

USER CONTROLS
Custom user controls are one way to begin sharing code between WPF and Silverlight
applications. Controls built completely in code would work the most seamlessly, provided that
any specific Silverlight or WPF code is cordoned off with the use of compiler directives. There
may be some issues in sharing XAML directly due to differences in the xmlns declarations.

PARTIAL CLASSES
Version 2.0 of the .Net Framework implemented a feature known as partial classes. Essentially,
a partial class tells the .Net compiler that additional implementation exists in a separate file;
thus, allowing a developer to organize their classes across multiple files.

When developing for Silverlight and WPF, partial classes could be used to organize a class into
three files: the common code, the WPF-only code, and the Silverlight-only code. The WPF
project, of course, would include the common code partial class as well as the WPF-only partial
class; likewise, the Silverlight project would contain the common code and the Silverlight-only
partial classes.

Generally speaking, both the WPF and Silverlight partial classes should contain implementations
of the same methods and properties. This will insure that the main code base will function
correctly without having to know which class implementation it is working with.

EXTENSION METHODS
New to version 3.0 of the .Net Framework are extension methods. Extension methods are static
methods contained within a static class and have a particular method signature. These methods
essentially, add functionality to existing value types or classes.

When developing for both Silverlight and WPF, developers could create two separate extension
classes: one for WPF and one for Silverlight. Each project would contain their respective
extension classes containing platform specific instructions.

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Unfortunately, the implementation of an extension method is different between Visual Basic
and C#. For example, to add a method called, GetPhysicalSize() to a Label, the following
extension method can be used.

C#

public static class ExtensionMethods
{
public static Size GetPhysicalSize(this Label label)
{
label.Measure(new Size(double.PositiveInfinity,
double.PositiveInfinity));

return new Size(label.ActualWidth, label.ActualHeight);
}
}

VISUAL BASIC

Public Module ExtensionMethods

<Extension()> _
Public Function GetPhysicalSize(ByVal l As Label) As Size
l.Measure(New Size(Double.PositiveInfinity, Double.PositiveInfinity))
Return New Size(l.ActualWidth, l.ActualHeight)
End Function

End Module

COMPILER DIRECTIVES
Compiler directives are embedded commands to instruct the compiler how to compile a certain
section of code, also known as conditional compilation. At compile-time the conditional
statements are evaluated and the proper code fragments are incorporated into the assembly.

Silverlight defines the boolean SILVERLIGHT compiler directive. This directive can be used to
segment code that performs differently between the two platforms.

#if SILVERLIGHT
// Perform Silverlight-only tasks.
#else
// Perform WPF-only tasks.
#endif

LINKED FILES
Silverlight projects implement a separate CLR than WPF projects. Therefore, it is not possible to
share sub-projects, such as a shared library, across applications. One solution to reuse code in

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both platforms would be to link files through Visual Studio into new sub-projects for each
application.

CODING SCENARIOS
There are several scenarios when coding for both platforms that require some forethought in
order to reduce code redundancy. While this whitepaper outlined many of the differences and
similarities between the two platforms, the following section details some of the more common
development areas where the differences between the two platforms become problematic
when trying to share code.

Element-to-Element Binding
WPF supports element-to-element binding to facilitate designing the UI when controls rely on
values from other controls. However, since Silverlight 2 does not support element-to-element
binding, developers should concentrate on creating an intermediate class to store the values
needed by all the controls and then bind the controls to that class. Developers familiar with
design patterns will recognize this methodology as a form of the model-view-presenter (MVP)
pattern.

For example, assume that a CheckBox control is responsible for enabling a group of controls. In
WPF, simple element-to-element binding can set the IsEnabled property of the parent control.
However, since Silverlight supports neither element-to-element binding nor the self-
propagating IsEnabled property, an intermediate class could be used to store this setting.

The custom class could be constructed as follows:

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C#

public class CustomSettings : INotifyPropertyChanged
{
private bool _isEnabled = false;

public bool IsEnabled
{
get { return _isEnabled; }
set
{
_isEnabled = value;
NotifyPropertyChanged("IsEnabled");
}
}

// Snip remainder of implementation...

VISUAL BASIC

Public Class CustomSettings

Private _isEnabled As Boolean = False

Public Property IsEnabled() As Boolean
Get
Return _isEnabled
End Get
Set(ByVal value As Boolean)
_isEnabled = value
NotifyPropertyChanged("IsEnabled")
End Set
End Property

' Snip remainder of implementation

The sample XAML for the Silverlight Page might appear as follows:



<UserControl.Resources>
<local:CustomSettings x:Key="MySettings" />
</UserControl.Resources>



<StackPanel DataContext="{StaticResource MySettings}">
<CheckBox Content="Is Enabled?"
IsChecked="{Binding IsEnabled, Mode=TwoWay}" />

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<Button x:Name="btnClick1" Content="Click Me 1" Width="150" Height="29"
IsEnabled="{Binding IsEnabled}" />
<Button x:Name="btnClick2" Content="Click Me 2" Width="150" Height="29"
IsEnabled="{Binding IsEnabled}" />
</StackPanel>

Silverlight 3 Note
The next version of Silverlight will support element-to-element binding. However, it may be desirable to
separate the data model from the view. Several design patterns, including a new variation of the MVP
pattern called Model-View-View Model (MVVM), recommend that approach.

Multi-Data Binding
Since Silverlight does not support multi-data binding, developers needing cross-platform
support should build their application to the lowest common denominator. Building a separate
class to aggregate the multiple values would mimic the WPF functionality. Both Silverlight and
WPF can react to classes supporting INotifyPropertyChanged and parse the multiple values
correctly in a ValueConverter.

Taking the Person class from earlier where multi-data binding is needed for when either the first
name or last name changes:

C#

public class Person : INotifyPropertyChanged
{
// Implementation snipped for brevity.

public string FullName
{
get { return _firstName + " " + _lastName; }
}

}

VISUAL BASIC

Public Class Person

' Implementation snipped for brevity.

Public ReadOnly Property FullName() As String
Get
Return _firstName & " " & _lastName
End Get
End Property
End Class

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A corresponding ValueConverter to return the first and last names concatenated into a string in
the form of “lastname, firstname”:

C#

public class NameConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter,
CultureInfo culture)
{
// Error checking omitted...

string[] names = ((string) value).Split(' ');

return string.Concat(names[1], ", ", names[0]);
}

// ConvertBack method snipped for brevity.

}

VISUAL BASIC

Public Class NameConverter
Implements IValueConverter

Public Function Convert(ByVal value As Object, _
ByVal targetType As System.Type, _
ByVal parameter As Object, _
ByVal culture As CultureInfo) _
As Object Implements IValueConverter.Convert

' Error checking omitted...
Dim names() As String = CType(value, String).Split(" ")

Return String.Concat(names(1), ", ", names(0))

End Function

' ConvertBack method snipped for brevity.

End Class

Triggers / Visual State Manager
Adding UI effects to controls can be one of the most troublesome areas to reduce code
redundancy. WPF supports various triggers to obtain visual effects while Silverlight implements
a Visual State Manager. WPF only supports the Visual State Manager in the WPF Toolkit, and at
the time of this writing, is only in beta. Using the VSM would yield the most mode reuse
between the two platforms, assuming the WPF Toolkit has been installed.

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See the earlier section on the Visual State Manager for an example code snippet.

Fonts
Silverlight has the capability of obtaining fonts in many different ways: from embedding as a
resource within the assembly, or externally loaded via an asynchronous web request. WPF can
use any font resource available on the Windows system without these extra steps. Since adding
fonts to Silverlight applications can increase the size of the application’s footprint, it is
recommended to judiciously embed fonts and instead download them asynchronously when
needed.

Asynchronously loading a font follows the same methodology as loading any asset
asynchronously. In the case of a font, however, one needs to set the FontSource property to the
incoming stream, and set the FontFamily to choose the font from the source.

C#

private void LoadFont()
{
WebClient wc = new WebClient();
wc.OpenReadCompleted += new
OpenReadCompletedEventHandler(wc_OpenReadCompleted);
wc.OpenReadAsync(new Uri("/Assets/myfont.ttf", UriKind.Relative));
}

void wc_OpenReadCompleted(object sender, OpenReadCompletedEventArgs e)
{
this.txtMessage.FontSource = new FontSource(e.Result);
this.txtMessage.FontFamily = new FontFamily("Custom Font");
}

VISUAL BASIC

Private Sub LoadFont()
Dim wc As New WebClient
AddHandler wc.OpenReadCompleted, AddressOf wc_OpenReadCompleted
wc.OpenReadAsync(New Uri("/Assets/myfont.ttf", UriKind.Relative))
End Sub

Private Sub wc_OpenReadCompleted(ByVal sender As Object, _
ByVal e As OpenReadCompletedEventArgs)

Dim fs As FontSource = New FontSource(e.Result)

Me.txtMessage.FontSource = fs
Me.txtMessage.FontFamily = New FontFamily("Custom Font")
End Sub

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SUMMARY
WPF and Silverlight provide a new paradigm for application development using the same core
technology of declarative XAML and the well-known code-behind model for procedural code. Silverlight,
generally considered to be a subset of WPF, has been moving closer in implementation with each
successive release. However, since Silverlight runs as an application within the plug-in model of a
browser, it will always be hampered in some ways that will require innovative thinking to work around:
whether in code or in application design. Future releases of both Silverlight and WPF have been making
advancements to close the distance in the differences between the two platforms.

Almost as proof, with the upcoming release of Silverlight 3, many differences are either outright
removed, or mitigated. In addition, Silverlight 3 will sport some new and interesting features (see
http://silverlight.net/getstarted/silverlight3/default.aspx for more information).

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Microsoft Wpf Silverlight Comparison Whitepaper V1 1

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Microsoft Wpf Silverlight Comparison Whitepaper V1 1